There is a SETTINGS tab on the bottom of the main menu page.
...
When collecting Momentary Time Sample data for skills and behaviors, you have the option to change the default response to intervals without data entered. When you receive the notification that the interval has ended, and no response is entered you have the option to have those intervals automatically scored as Y (Yes, the behavior occurred), N (No, the behavior did not occur), or C (Cancel/discard the interval). The default will be set to C (Cancel/discard the interval), but can be changed in the settings tab or at the individual program level for both skills and behaviors.
...
Please note that the MTS default setting will be locked once the timer has started at the individual skill or behavior program. You can change the default MTS setting at any point, for future intervals, if the timer is turned on and it will change the default for future intervals.